Optically isolated signal coupler with linear response

Abstract

An optocoupler for isolating electrical signals that translates an electrical input signal linearly to an electrical output signal. The optocoupler comprises a light emitter, a light receiver, and a light transmitting medium. The light emitter, preferably a blue, silicon carbide LED, is of the type that provides linear, electro-optical conversion of electrical signals within a narrow wavelength range. Correspondingly, the light receiver, which converts light signals to electrical signals and is preferably a cadmium sulfide photoconductor, is linearly responsive to light signals within substantially the same wavelength range as the blue LED.

What is claimed is: 
     
       1. Apparatus for optically isolating electric signals, said apparatus for use with an electrical input system and an electrical output system, said apparatus comprising: a light emitting diode made of silicon carbide, said light emitting diode responsive to electric input signals from said input system and converting said electric input signals to light signals; and   means in spaced relationship to said light emitting diode for receiving light, said light receiving means responsive to said light signals and converting said light signals to electrical output signals, said electric output signals proportional to said electric input signals, said light receiving means in electrical communication with said output system.   
     
     
       2. The apparatus as recited in claim 1, wherein said light emitting diode emits light within a first wavelength range and having an intensity proportional to said input signal. 
     
     
       3. The apparatus as recited in claim 1, wherein said light receiving means receives light having an intensity and within a first wavelength range, said light receiving means converting said light received to electrical output signals proportional to said light intensity. 
     
     
       4. The apparatus as recited in claim 1, wherein said light emitting diode emits light within a wavelength range of between 415 and 565 nanometers with an intensity having a maximum at a wavelength approximately 470 nanometers. 
     
     
       5. The apparatus as recited in claim 1, wherein said light receiving means is linearly responsive to light having a wavelength of no more than 513 nanometers. 
     
     
       6. The apparatus as recited in claim 1, wherein said light emitting diode is a blue light emitting diode, said diode emitting light having a wavelength within the range from approximately 415 nanometers to approximately 565 nanometers. 
     
     
       7. The apparatus as recited in claim 1, wherein said light receiving means further comprises a photoconductive cell. 
     
     
       8. The apparatus as recited in claim 1, wherein said light receiving means is made of cadmium sulfide. 
     
     
       9. The apparatus as recited in claim 1, further comprising diode for transmitting light between said light emitting means and said light receiving means, said light transmitting means in optical communication with said light emitting means and said light receiving diode and positioned therebetween. 
     
     
       10. The apparatus as recited in claim 1, further comprising means for transmitting light, said light transmitting means made of a heat-resistant material and having a first side and an opposing second side, said first side having said light emitting diode deposited thereon, said second side having said light detecting means deposited thereon. 
     
     
       11. The apparatus as recited in claim 1, further comprising diode for holding said light emitting means, said light transmitting means and said light receiving means in fixed space relation, said holding means having a first side in electrical communication with said input system and an opposing second side in electrical communication with said output system. 
     
     
       12. The apparatus as recited in claim 1, further comprising a transparent fiber for transmitting light, said light transmitting fiber having a first end in optical communication with said light emitting diode and a second end in optical communication with said light receiving means. 
     
     
       13. The apparatus as recited in claim 1, further comprising a means for transmitting light, said light transmitting means having a first system of lenses and a second system of lenses, said first system of lenses positioned so that said light signals from said light emitting diode passes therethrough, said second system of lenses positioned so that said light signals passing through said first system of lenses passes through said second system of lenses to said light receiving means. 
     
     
       14. An optocoupler for isolating electrical signals between an electrical input system and an electrical output system, said apparatus comprising: a blue light emitting diode made of silicon carbide, said light emitting diode responsive to input signals from said input system and converting said input signals to light signals having an intensity and a wavelength within the range from approximately 415 nanometers to approximately 565 nanometers;   a photoconductive cell in spaced relationship to said light emitting diode, said photoconductive cell made of cadmium sulfide and linearly responsive to said intensity of said light signals having a wavelength of no more than approximately 513 nanometers and converting said light signals to electrical output signals, said electric output signals proportional to said electric input signals, said photoconductive cell in electrical communication with said output system; and   means for transmitting light between said light emitting diode and said photoconductive cell, said light transmitting means in optical communication with said light emitting diode and said photoconductive cell and positioned therebetween.   
     
     
       15. The apparatus as recited in claim 14, wherein said light emitting diode emits light within a first wavelength range and said photoconductive all receives light within said first wavelength range, said light intensity proportional to said electrical input signals, said electrical output signals proportional to said light intensity. 
     
     
       16. The apparatus as recited in claim 14, wherein said blue light emitting diode emits light within a wavelength range of between 415 and 565 nanometers with said light intensity having a maximum at a wavelength approximately 470 nanometers. 
     
     
       17. The apparatus as recited in claim 14, wherein said photoconductive cell is responsive to light having a wavelength of no more than approximately 513 nanometers. 
     
     
       18. The apparatus as recited in claim 14, further comprising means for holding said light emitting diode, said light transmitting means and said photoconductive cell in fixed space relation, said holding means having a first side in electrical communication with said electrical input system and an opposing second side in electrical communication with said electrical output system.